1. Field of the Invention
The present invention relates to a steering damper system for use on a vehicle, and to a saddle riding type vehicle equipped with the steering damper system.
2. Description of the Related Art
Conventionally, a hydraulic damper is well known as a steering damper mounted on a saddle riding type vehicle. The hydraulic damper uses a damping force generated when hydraulic oil in an oil chamber passes through an orifice, and can obtain a damping force according to a steering angle speed. Recently, steering damper systems of the electronically controlled type have been disclosed. See Japanese Unexamined Patent Publication No. 2003-170883 (pages 3-6, FIGS. 1 and 2) and Japanese Unexamined Patent Publication S63-64888 (pages 3-4, drawings), for example.
When a steering angle speed of the handlebars in Japanese Unexamined Patent Publication No. 2003-170883 is equal to or less than a first threshold, a relatively small damping force is generated and this damping force is adjusted according to a vehicle speed. When a steering angle speed exceeds the first threshold and is equal to or less than a second threshold, a medium damping force is generated and this damping force is adjusted according to the steering angle speed. When a steering angle speed exceeds the second threshold, a large damping force is generated and this damping force is adjusted according to the steering angle speed.
When a vehicle speed and a steering angle in Japanese Unexamined Patent Publication S63-64888 exceed predetermined threshold limit values, a control device will control a buffer to increase a damping force.
Both techniques described in Japanese Unexamined Patent Publication No. 2003-170883 and Japanese Unexamined Patent Publication S63-64888 adjust damping forces according to vehicle speeds. However, it can hardly be said that these techniques are fully satisfactory with regard to both the rider's burden and controllability in steering operations. When a relatively large steering control is required during a high-speed run, such as when the vehicle negotiates a corner at high speed, for example, a large damping force generated according to the vehicle speed will deprive the rider of a natural feeling of operation. Conversely, a lowering of the function to adjust the damping force according to the vehicle speed will increase the rider's burden for stabilizing a steering operation during a high-speed run. Further, when the vehicle jumps as does an off-road vehicle, the rider turns the handlebars to a large degree in the air to control the vehicle. At such times, a large damping force will result in a heavy steering operation, thereby worsening the feeling of the steering operation.